Abstract

OWLlink provides a declarative interface for – among other
things – asserting OWL axioms to a Knowledge Base (KB) of an
OWL reasoner. This OWLlink extension adds the ability to retract
previously asserted axioms from KBs.

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Earlier drafts of the OWLlink specification have been published by the informal
OWLlink working group at http://www.owllink.org.

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Table of Contents

1 Introduction

The OWLlink core interface [OWLlink Structural
Specification] relies on a certain kind of incremental
batch-oriented reasoning procedure. After submission of a set of
axioms a client can pose some queries, add further axioms, query
again, and so on. Deletion of axioms is ony possible by releasing a
KB and re-submission of axioms. This document describes the
retraction extension of OWLlink which allows to retract previously
told KB fragments on axiom level.

This extension is based on the same preliminaries than the
OWLlink core.

2 Retraction

The Retract request is the inverse
command to Tell (cf. Section ‘4
Tells’ [OWLlink Structural
Specification]) and takes a set of OWL 2 axioms (cf.
Section ‘9 Axioms’ [OWL 2 Structural
Specification]) and removes them from the respective KB
as shown in Figure 1. The removal must be
sensitive to the rules of structural equivalence of OWL 2. That is,
an axiom can only be removed from a KB if and only if the KB
contains an axiom which is structural equivalent to the one given
in the retraction request. A server must not respond with an error
if a KB does not contain a structurally equivalent axiom but is
free to provide a warning. If all axioms of a retraction request
are successfully removed from the KB, the server has to respond
with an OK response.

Figure 1. Retraction Request (the
Tell request is rendered
semi-transparently to show the symmetry)